My son (3 years old) and I went to the beach twice this weekend and now he is vomiting, warm (not a high temp.), and achy. I m not sure if it is heat exhaustion, but this happened last summer when we went to the beach he had vomiting, high temp., and diarrhea. It also happens if he is outside for more than a couple hours, a few days in a row. I am not sure what to do, he just seems to get sick after being out in the sun and we always give him water, what can I do to prevent this from happening?